Latex emulsions of resins may be produced using PIE processes in which resins are dissolved in a mixture of water, a base and organic solvent(s) (e.g., methyl ethyl ketone (MEK), isopropyl alcohol (IPA) or both) to form a water-in-oil (W/O) dispersion (i.e., water droplets dispersed in continuous oil). Subsequently, water is added to convert the dispersion into an oil-in-water (O/W) dispersion. In embodiments, liquids from a prior PIE can be reused in a subsequent PIE.
Amorphous polyester latexes may be produced in a solvent reuse process with organic distillate from a previous PIE. The solvent(s), such as, methyl ethyl ketone (MEK) and isopropyl alcohol (IPA), from a latex emulsion can be distilled under vacuum and be used as solvent of a resin in a subsequent PIE. Solvent reuse processes provide savings in raw material, solvents(s), cost and solvent disposal fees, leading to significant reduction, of production cost.
When IPA is used as a solvent, particle size of amorphous resins is determined primarily by the amount of IPA. When ammonium hydroxide or ammonia is used as the base, the amount of ammonium hydroxide or ammonia impacts the neutralization ratio of crystalline polyester (CPE) resins and CPE particle size. Thus, for CPE PIE, where an objective is to employ solvent reuse and to avoid solvent disposal fees, base amounts must be considered and carefully controlled.